Dosimetric inter-institutional comparison in European radiotherapy centres: Results of IAEA supported treatment planning system audit

Gershkevitsh, E.; Pesznyák, Csilla; Petrović, Borislava; Grezdo, J.; Chełmiński, K.; Lopes, Maria do Carmo; Iżewska, J.; Dyk, Jacob Van

doi:10.3109/0284186x.2013.840742

Cited by 25 publications

(16 citation statements)

References 17 publications

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“…The Level III audits in this work are conducted on onsite audits using directly PSL calibrated Farmer type ionization chambers and electrometers resulting in low measurement uncertainties and allowing for tight action-level tolerances. The contribution of other factors, such as incorrect beam modelling and input data as reported in Gershkevitsh et al [33] may also have contributed to the oversight of the systematic nature of the discrepancy.…”

Section: Discussionmentioning

confidence: 91%

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National dosimetric audit network finds discrepancies in AAA lung inhomogeneity corrections

Dunn¹,

Lehmann

Lye³

et al. 2015

Physica Medica

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This work presents the Australian Clinical Dosimetry Service's (ACDS) findings of an investigation of systematic discrepancies between treatment planning system (TPS) calculated and measured audit doses. Specifically, a comparison between the Anisotropic Analytic Algorithm (AAA) and other common dose-calculation algorithms in regions downstream (≥2cm) from low-density material in anthropomorphic and slab phantom geometries is presented. Two measurement setups involving rectilinear slab-phantoms (ACDS Level II audit) and anthropomorphic geometries (ACDS Level III audit) were used in conjunction with ion chamber (planar 2D array and Farmer-type) measurements. Measured doses were compared to calculated doses for a variety of cases, with and without the presence of inhomogeneities and beam-modifiers in 71 audits. Results demonstrate a systematic AAA underdose with an average discrepancy of 2.9 ± 1.2% when the AAA algorithm is implemented in regions distal from lung-tissue interfaces, when lateral beams are used with anthropomorphic phantoms. This systemic discrepancy was found for all Level III audits of facilities using the AAA algorithm. This discrepancy is not seen when identical measurements are compared for other common dose-calculation algorithms (average discrepancy -0.4 ± 1.7%), including the Acuros XB algorithm also available with the Eclipse TPS. For slab phantom geometries (Level II audits), with similar measurement points downstream from inhomogeneities this discrepancy is also not seen.

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Section: Discussionmentioning

confidence: 91%

“…A large European study by Gershkevitsh et al [33] conducted TPS audits in 60 radiotherapy centres using the TECDOC 1583 methodology also employed in the Level III audit presented here. In total, 190 data sets (combination of algorithm and beam quality) were collected and analysed.…”

Section: Discussionmentioning

confidence: 98%

National dosimetric audit network finds discrepancies in AAA lung inhomogeneity corrections

Dunn¹,

Lehmann

Lye³

et al. 2015

Physica Medica

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“…Accurate calculations of dose and dose gradients are especially important for treatments where ablative doses of radiation are delivered to targets in close proximity to critical structures, such as spine SABR treatments. Dose calculation accuracy is known to be detrimentally affected by the use of suboptimal beam configuration data in the radiotherapy treatment planning system (TPS) and by the inappropriate handling of simplifications in the TPS model …”

Section: Introductionmentioning

confidence: 99%

Optimization of the dosimetric leaf gap for use in planning VMAT treatments of spine SABR cases

Middlebrook¹,

Sutherland²,

Kairn

2017

J Applied Clin Med Phys

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The dosimetric leaf gap (DLG) is a beam configuration parameter used in the Varian Eclipse treatment planning system, to model the effects of rounded MLC leaf ends. Measuring the DLG using the conventional sliding‐slit technique has been shown to be produce questionable results for some volumetric modulated arc therapy (VMAT) treatments. This study therefore investigated the use of radiochromic film measurements to optimize the DLG specifically for the purpose of producing accurate VMAT plans using a flattening‐filter‐free (FFF) beam, for use in treating vertebral targets using a stereotactic (SABR, also known as SBRT) fractionation schedule. Four test treatments were planned using a VMAT technique, to deliver a prescription of 24 Gy in 3 fractions to four different spine SABR treatment sites. Measurements of the doses delivered by these treatments were acquired using an ionization chamber and radiographic film. These measurements were compared with the doses calculated by the treatment planning system using a range of DLG values, including a DLG identified using the conventional sliding‐slit method (1.1 mm). An optimal DLG value was identified, as the value that produced the closest agreement between the planned and measured doses (1.9 mm). The accuracy of the dose calculations produced using the optimized DLG value was verified using additional radiochromic film measurements in a heterogeneous phantom. This study provided a specific initial DLG (1.9 mm) as well as a film‐based optimization method, which may be used by radiotherapy centers when attempting to commission or improve an FFF VMAT‐based SABR treatment programme.

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“…A number of official publications, 1,2 papers 3-8 and verification audits [9][10][11] confirm that the commissioning of the treatment planning system (TPS) is very important in radiation therapy. On the one hand, this task requires at least a basic control of TPS, and on the other hand, performing the verification of measurements involves consideration and preparation.…”

Section: Introductionmentioning

confidence: 99%

Determination of boundaries between ranges of high and low gradient of beam profile

Wendykier

Bieniasiewicz

Grządziel

et al. 2016

Reports of Practical Oncology & Radiotherapy

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Dosimetric inter-institutional comparison in European radiotherapy centres: Results of IAEA supported treatment planning system audit

Cited by 25 publications

References 17 publications

National dosimetric audit network finds discrepancies in AAA lung inhomogeneity corrections

National dosimetric audit network finds discrepancies in AAA lung inhomogeneity corrections

Optimization of the dosimetric leaf gap for use in planning VMAT treatments of spine SABR cases

Determination of boundaries between ranges of high and low gradient of beam profile

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